Vanadium-zinc borate solder glasses



May 27, 1969 B. v. JANAKIRAMA-RAO 3,446,695

VANADIUM-ZINC BORATE SOLDER GLASSES Filed Oct. 3, 1966 LINEAR COEFFICIENT OF EXPANSION IO OI23456789IOIII2 WEIGHT PERCENT OXIDE INVENTOR.

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United States Patent US. Cl. 161-192 11 Claims The present invention pertains to novel glass compositions, and more particularly, the instant invention pertains to vitreous sealing glass compositions for fabricating glass-to-glass or glass-to-metal seals. Specifically, the instant invention pertains to vitreous sealing glass compositions having a relatively low thermal coefiicient of expansion and a relatively low fiber softening point temperature.

The art of forming glass-to-glass or glass-to-metal seals is fraught with many problems. Among the problems faced in the sealing art is the poor mismatch of the coeificients of thermal expansion of the solder glass sealant with the sealable base glass or metal. Another problem is the inability of the sealing glass composition to intimately fuse to the sealable surface at a substantially lower fusible temperature than the deformation or distortion temperature of said sealable glass or metal. Accordingly, it will be appreciated by those versed in the art that a solder glass possessing an elfective coefficient of expansion which is essentially equal to the coefiicient of expansion of the surfaces to be bonded and suitable for fabricating satisfactory seals represents a valuable contribution to the sealing art. Also, it will be appreciated by those skilled in the art that solder glass compositions possessing low fiber softening point temperatures which lend themselves to successful sealing procedures would represent a contribution to the art and have a positive economic value.

Accordingly, it is an object of the present invention to provide novel glass compositions.

A further object of the invention is to provide novel solder glass compositions.

It is a further object of the present invention to provide solder glasses having a relatively low coefficient of thermal expansion.

Yet a further object of the present invention is to provide solder glasses suitable for sealing to metals and or glass possessing a relatively low coefiicient of thermal expansion.

Another object of the present invention is to provide solder glasses having a relatively low fiber softening point temperature.

Yet a further object of the invention is to provide glassto-glass or glass-to-metal seals.

Other objects, as well as advantages of the instant invention, will become apparent from a consideration of the accompanying specification and claims, as well as in connection with the accompanying drawing.

According to the present invention there is provided a family of vitreous sealing glass compositions having an expansion coefficient (0300 C.), in the range of 40 to 50x10 in./in./ C. and a fiber softening point temperature of about 525 to 575 C. The glass compositions of the present invention are based on a ZnOB O system in which V 0 is substituted for part of ZnO to produce a V O -ZnO-B O glass system which latter system can also include the glass forming oxides CuO, PbO, Si0 and A1 0 The novel subject glasses of the instant invention generally contain 5 to 30 weigh-t percent V 0 20 to 40 weight percent B 0 40 to 60 weight percent ZnO and l to weight percent CuO. In addition, the V O -ZnO-B O glass system can contain 0 to 7.5 weight percent PbO, 0 to 0.2 weight percent F, 0 to 10 weight percent Si0 and 0 to 10 weight percent A1 0 Exemplary vitreous glasses of the subject invention are the following: (a) a glass containing 5 to 15 weight percent V 0 20 to 30 weight percent B 0 40 to 60 weight percent ZnO and 2 to 10 weight percent CuO; (-b) a vitreous solder glass consisting essentially of 5 to 15 weight percent V 0 20 to 30 weight percent B 0 40 to 60 weight percent ZnO, 2 to 10 weight percent CuO, and 1 to 7.5 weight percent PbO; (c) a vitreous glass composition consisting essentially of 5 to 15 weight percent V 0 20 to 30 weight percent B 0 40 to 60 weight percent ZnO, 2 to 10 weight percent CuO, 1 to 7.5 weight percent PbO and 0.2 to 1 weight percent PbF (d) a glass consisting essentially of 5 to 15 weight percent V 0 20 to 30 Weight percent B 0 40 to 60 weight percent ZnO, 2 to 10 weight percent CuO, 1 to 7.5 Weight percent PbO, 1 to 5 Weight percent SiO (e) a vitreous solder glass containing 8 to 10 weight percent V 0 24 to 30 weight percent B O 50 to 60 weight percent ZnO, 2 to 5 weight percent CuO, 1 to 5 Weight percent Si0 and 1 to 3 weight percent PbO; (f) a vitreous solder glass containing 5 to 15 weight percent V 0 20 to 30 weight percent B 0 40 to 60 weight percent ZnO and 2 to 10 weight percent CuO; (g) a vitreous solder glass containing 5 to 30 weight percent V 0 20 to 40 weight percent B 0 40 to 60 weight percent ZnO and 1 to 7.5 weight percent PbO; and a glass consisting essentially of 8 to 10 weight percent V 0 24 to 30 weight percent B 0 50 to 60 weight percent ZnO, 2 to 5 weight percent CuO, 1 to 5 weight percent SiO and 1 to 3 weight percent PbO; (h) a vitreous solder glass containing 5 to 15 weight percent V 0 20 to 30 weight percent B 0 40 to 60 Weight percent ZnO and 2 to 10 weight percent CuO; (i) a vitreous solder glass containing 5 to 30 Weight percent V 0 20 to 40 Weight percent B 0 40 to 60 Weight percent ZnO and 1 to 7.5 weight percent PbO; (j) and a glass consisting es sentially of 8 to 10 weight percent V 0 24 to 30 weight percent B 0 50 to 60 weight percent ZnO and 3 to 5 Weight percent PbO.

In a particular and important embodiment of the subject invention there are provided glass compositions having a coefiicient of thermal expansion (0 to 300 C.) of about 44 to 50x10 in./in./ C. and a fiber softening point temperature of 525 to 575 C. The glass compositions possessing this low coefiicient of thermal expansion and low fiber softening point temperature appear to be unobvious since, by comparison, a composition containing 60 weight percent ZnO and 40 weight percent B 0 has a coefiicient of expansion of 50 10-' in./in./ C. and a fiber softening point of 650 C. It has now unexpectedly been found that the replacement of part of ZnO by V 0 to give a ZnO-B O -V O system and the addition of CuO or PbO to the newly formed ZnO-B O -V O system lowers the fiber softening point to less than 575 C. and at the same time substantially decreases the coefficient of thermal expansion to less than 50 X10- in./in./ C. This dual behavior appears to be exceptional and is not seen to be common for ordinary glass systems. Generally, the coefficient of expansion of the present glasses will be in the range of 44 to 48 l0' in./in./ C. and the fiber softening point temperature for said glasses in the range of 525 to 575 C. The addition of PbO in the amounts up to 5 weight percent to the ZnO-B O -V O system does not materially change the linear coefficient of thermal expansion of the glass system while larger amounts, generally, in excess of 10 Weight percent PbO, tends to increase the coeflicient of thermal expansion. The addition of PbO to the same system in amounts up to about 7.5 weight percent tends to lower the fiber softening point temperature. The addition of PbO, generally in amounts up to 7.5 weight percent, to the ZnO-B O -V O CuO glass tends to produce a glass characterized by both a decreased coefiicient of thermal expansion in the range of 44 to 50 l()-' in./in./ C. and softening point tem- In Table No. 2, immediately below, is listed the oxides, perature in the range of 525 to 575 C. The changes in the expressed in weight percent, and physical charactercoefficient of thermal expansion produced by the addition istices for each glass prepared from the batch ingredients of CuO or PbO to the ZnO-B O -V O system are further set forth as Examples 2 to 13 in Table No. 1 above. The set forth in the accompanying drawing. examples corresponding to those glasses are set forth as In preparing the novel vitreous sealing glass composi- 5 Examples No. 14 to 25 respectively. In Table 2 F.S.P. tions of the present invention, the batch ingredients are is used to designate the fiber softening point and intimately mixed by hand, or in a commercially available oc(0300 C.) X represents the linear coeflicient of blender, and heated to a temperature such that all the thermal expansion in in./in./ C.

TABLE 2.COMPOSITION, WEIGHT PERCENT Example No.

Component 14 15 16 17 1s 10 20 21 22 23 24 25 7205 V c a a 10 2O 50 9. 5 17 BgOa .4 8.6 ZnO 7.1 (7110 2. PbO 1. SK); 0. A120 a(O-300 c.) 10 45 44 57 45 47 49 R8,? 575 570 560 570 560 550 650 575 525 480 575 553 glass forming substances are present in a molten state, The glass compositions of the instant invention are thereby enabling the formation of a glass from a homoused as vitreous solder glass sealants for assembling glassgeneous melt. Generally, the batch ingredients were well 25 toglass or glass-to-metal parts by conventional methods mixed by hand and melting was done in a 90% platinum known to the art. The vitreous sealing glasses can be --l0% rhodium or fused silica crucible, in an electric applied by both the hot and cold sealing techniques. furnace at about 1100 C. to 1300 C., for about A When the cold procedure is employed, the solder glass to 2 hours in an air atmosphere. The batch ingredients composition is ground and mixed with a suitable vehicle were continuously stirred and agitated during the melting to form a paste. One acceptable vehicle is composed of and heating procedures. about 1 to 3%, usually about 1 to 2% nitrocellulose The batch materials employed for preparing the glasses in amyl acetate. Other acceptable organic binders or of the subject invention were of a high degree of purity vehicles may be employed provided they will readily and were selected from the following commercially availburn off and volatize during the heating procedure in the able materials: silicon dioxide (SiO Kona Quintus thermal sealing of the preformed parts. In addition, the Quartz or Ottawa Sand, aluminum oxide (A1 0 Alcoa selected organic binder should not react with any of the A-14 or aluminum trihydroxide, zinc oxide (ZnO), vanaelements making up the bonded assembly. Among exdium pentoxide (V 0 cupric oxide (CuO), cupro-us amples of other organic binders which can be used are oxide (C11 0), lead fluoride (PbF lead oxide (PbO) those which include gelatin dissolved in water, nitroceland boric acid (H BO Of course, functionally equivalulose and butyl acetate, camphor with cellulose, and

lent oxides, carbonates, fluorides, silicates, or any other the like.

form which does not disturb or adversely effect the sub- The vitreous solder glass composition, mixed with the ject glass composition may be utilized for forming the vehicle, can be manually or mechanically applied by subject glasses. using a spatular, extrusion, cold, dip brush, roller coat, Example 1 spray, doctor blade or any like means. In the extrusion procedure, a toothpaste-like mixture of solder glass and carrier can be used to apply a uniform layer along at least one of the edges to be sealed.

After coating at least one of the surfaces to be sealed with the vitreous sealing glasses of the invention and em- Crucible at about 10000 to 11005 C for about 1 hour. ploying any of the sealing techniques discussed supra, the

The theoretical composition for the glass thus produced coatiid Parts can be dned in an Oven or by any Suitable is 10 weight percent V 0 30 weight percent B 0 58 i i procedure the dry assembled. parts are Weight percent ZnO and 2 Weight Percent C110. The glass intimately bonded in an oven or by any suitable heat had a coefficient of thermal expansion of 46 10 procedure finally cooled to telPPemturein./in./ C. and a fiber softenin point temperature of The following examples lnustratwe i glass'to' C glass or glass-to-metal seals WhlCh were fabricated with The following table, Table No. 1, lists representative vitreous Sealing glass compositions of the Subject A vitreous sealing glass composition was prepared by intimately blending 10 grams of V 0 53.3 grams of H BO 58 grams of ZnO and 2 grams of CuO to obtain a substantially homogeneous mixture and then melting 50 the mixture in an electric heated furnace, in a platinum batch compositions, Examples No. 2 to Example No. 13, 60 vgntlon E 1 6 which were melted and formed into vitreous solder glass Xamp e 2 compositions according to the mode and manner of the A butt seal was effected with a vitreous solder glass present invention; that is, the ingredients were well-mixed of the instant invention wherein the solder glass was and melted in a platinum-rhodium crucible at about 1000 formed into a glass rod and consisted essentially of 9.5 C. for about 1 hour and with constant stirring during the weight percent V 0 28.6 weight percent 13 0 57.1 melting and forming procedure. weight percent ZnO, 2.4 weight percent CuO, 1.9 weight TABLE 1.-BATCH GRAMS Examples Ingredient 2 percent PbO, and 0.5 weight percent SiO and possessed a coeflicient of expansion of 45x10" in./in./C. The rod was ground on one of its ends to a flat planar surface by polishing said end on a 120 grit alundum polishing wheel. The resulting polished end rod was sealed in a gas-oxygen flame to a piece of glass rod that was made from a glass consisting essentially of 64.5 weight percent SiO 18.4 weight percent B 7.5 weight percent A1 0 3.3 weight percent K 0, 2.2 weight percent Na O, 2.8 weight percent BaO and 0.6 weight percent Li O and having a linear coefiicient of thermal expansion of about 47 10 in./in./C. (0-300 C.). The seal stress for the seal formed was about 150 p.s.i., tension.

Example 27 A seal was effected by intimately bonding to a glass rod made of 64.8 weight percent SiO 22.2 weight percent B O 4.9 weight percent A1 0 0.1 weight percent K 0, 7.3 weight percent Na O, 0.2 weight percent CaOiMgO, 0.5 weight percent Fe O and 0.4 weight percent CeO and having a linear coeflicient of thermal expansion of about 50 10 in./in./C. (0300 C.) a solder glass rod made of 9.5 weight percent V 0 28.6 weight percent B 0 57.1 weight percent ZnO, 2.4 weight percent CuO, 1.9 weight percent PbO and 0.5 weight percent SiO and having a coefiicient of thermal expansion of about 45 10-' in./in./C. (0300 C.) by heating in a gas-oxygen flame the ends of the two rods which were previously placed in intimate contact. The glass rods, or their respective ends, were ground to a flat planar end surface before the solder glass rod was finally sealed to the first-mentioned rod. The measured seal stress was about 850' p.s.i. compression.

Example 28 Other seals were made employing the glass rods and sealing glasses of Example 26 and Example 27. In effecting these seals an electric furnace was used for sealing and the heating rate was about 10 C. per minute. The seals were made at 607 C. for one hour, and were cooled at the rate of 5 C. per minute. The stress was measured and was as reported in the respective example supra.

Example 29 A glass-to-metal seal was made by bonding a vitreous sealing glass rod to a piece of Kovar metal. The sealing glass rod, consisting of 9.5 weight percent V 0 28.6 weight percent B 0 57.1 weight percent ZnO, 2.4 weight percent CuO, 1.9 weight percent PbO and 0.5 weight percent SiO and having a coefficient of thermal expansion of about 45 10 in./in./C. was ground to a flat planar surface on at least one of the ends and placed in intimate contact with a piece of Kovar metal. As is well known, Kovar is a trade-name for an alloy having the approximate composition, iron 54 weight percent, nickel 29 weight percent and cobalt 17 weight percent. The seal was made using a radio frequency generator, at 2100" F., and holding time of 25 seconds. The resulting seal was annealed in a tube furnace at 850 F. for minutes. After cooling to room temperature, the seal was ground and the surface upon being examined under a microscope appeared to be essentially-free of cracks. Next, the seal was immersed in boiling water for 15 seconds and then in 0 C. water for 15 seconds. The seal was then reexamined under the microscope and no cracks were observed. The immersion process was reversed and again no cracks were found upon microscopic examination. The seal stress appeared to be less than 500 p.s.i. tension.

Example 3-0 A glass-to-metal seal was made by intimately bonding a vitreous sealing glass rod to a piece of Kovar alloy. The sealing glass rod, consisting essentially of 17 Weight precent V 0 25 weight percent B 0 55 weight percent ZnO and 3 weight percent A1 0 and having a coeflicient of thermal expansion of 48 10- in./in./C. (0-300 Example 31 A glass-to-glass seal was made by intimately bonding a glass rod consisting of 64.5 weight percent SiO 18.4 weight percent B 0 7.5 weight percent Al O 3.3 weight percent K 0, 2.2 weight percent Na O, 0.1 weight percent CaO+MgO, 2.8 weight percent BaO and 0.6 weight percent to a vitreous glass sealing rod consisting of 17 weight percent V 0 25 weight percent B 0 55 weight percent ZnO, and 3 weight percent A1 0 by placing the ends of said rods in intimate contact and heating for 1 hour at 550-555 C. The seal was cooled at the rate of 5 C. per minute. The stress, after cooling, was 1000 p.s.i. compression.

The stress measurements were made by measuring the retardation of polarized light by means of a polarimeter. The retardation data was then used to calculate the stress in lbs. per square inch by the following well-known relationship wherein S is the stress in p.s.i., R is the retardation in millimicrons, l is the path of light in cm., and K is the factor 14.22 over the optical coefficient expressed in mu/cm./kg./cm.

The vitreoiis sealing glasses of the instant invention can be used to fabricate items of commerce. For example, alloy lead-in conductors can be sealed to a. glass encapsulating structure for effecting low seals in the vacuum sealing industry and the like.

The term metal as used herein includes metals, metallic alloys, and intermetallic compounds. The notation p.s.i. as used herein means pounds per square inch.

I claim:

1. A vitreous solder glass composition wherein said glass consists essentially of 5 to 30 weight percent V 0 2-0 to 40 weight percent B 0 40 to 60 weight percent ZnO, l to 10 weight percent CuO, 0 to 7.5 weight percent PbO, 0 to 10 weight percent SiO 0 to 10 weight percent A1 0 and 0 to 0.2 weight percent PbF and wherein said solder glass composition having a fiber softening point temperature of 525 to 575 C., and coefiicient of thermal expansion of 40 to 50x10- (0-300 C.).

2. A vitreous solder glass according to claim 1 wherein said glass consists essentially of 5 to 15 weight percent V 0 20 to 30 weight percent B 0 40 to 60 weight percent ZnO and 2 to 10 weight percent CuO.

3. A vitreous solder glass according to claim 2 wherein said glass contains from 2 to 8 weight percent CuO and has a coefficient of thermal expansion of 44 to 48 10- (0300 C.).

4. A vitreous solder glass according to claim 1 wherein said glass consists essentially of 5 to 15 weight percent V 0 20 to 30 weight percent B 0 40 to 60 weight percent ZnO, 2 to 10 weight percent CuO and 1 to 7.5 weight percent PhD.

5. A vitreous solder glass according to claim 1 wherein said glass consists essentially of 5 to 15 weight percent V 0 20 to 30 weight percent B 0 40 to 60- weight percent ZnO, 2 to 10 weight percent CuO, 1 to 7.5 weight percent PhD and l to 0.2 weight percent PbF 6. A vitreous solder glass according to claim 1 wherein said glass consists essentially of 5 to 15 weight percent V 0 20 to 30 weight percent B 0 40' to 60 weight percent ZnO, 2 to 10 weight percent CuO, 1 to 7.5 weight percent P-bO and l to 5 weight percent SiO 7. A vitreous solder glass according to claim 6 wherein said glass consists essentially of 8 to 10 weight percent V 0 24 to 30 weight percent B 0 50 to 60- weight 7 percent ZnO, 2 to 5 weight percent CuO, 1 to 3 Weight percent SiO and 1 to 3 weight percent PbO.

8. A vitreous solder glass composition wherein said glass consists essentially of 5 to 30 weight percent V 20 to 40 weight percent B 0 40 to 60 weight percent ZnO and 1 to 7.5 weight percent PbO and wherein said glass has a fiber softening point of 525 to 575 C., and a coefficient of expansion of 40 to 50x10- (O300 C.).

9. A vitreous solder glass composition according to claim 8 wherein said glass consists essentially of 8 to 10 weight percent V 0 24 to 30 weight percent B 0 50 to 60 weight percent ZnO and 3 to 5 weight percent PbO.

10. A composite article comprising preformed components and a layer of vitreous solder glass between said components and integrally bonded thereto, said vitreous solder glass consisting essentially of 5 to 30 weight percent V O 20 to 40 weight percent B 0 40 to 60 weight percent Z110, 1 to 10 weight percent CuO, 0 to 7.5 weight percent PbO, 0 to 10 weight percent SiO 0 to 0.2 weight percent PbF and wherein said vitreous sealing glass has a fiber softening point of 525 to 575 C. and a coefficient of thermal expansion of 40 to 50x10" (0300 C.).

11. Composite article comprising preformed components and a layer of a vitreous solder glass between said components and wherein said components have a thermal coetficient of thermal expansion sufficiently complemental to permit their integral bonding to said solder glass which consists essentially of 5 to weight percent V 0 20 to weight percent B 0 40 to weight percent ZnO and 1 to 7.5 weight percent PbO and wherein said solder glass has a. fiber softening point temperature of 525 C. to 575 C. and a coefficient of thermal expansion of 40 to 5() 10 (0300 C.).

References Cited UNITED STATES PATENTS 11/1962 Babcock 106-39 X 5/1963 Pirooz 106-53 US. Cl. X.R. 

1. A VITREOUS SOLDER GLASS COMPOSITION WHEREIN SAID GLASS CONSISTS ESSENTIALLY OF 5 TO 30 WEIGHT PERCENT V2O5, 20 TO 40 WEIGHT PERCENT B2O3, 4O TO 60 WEIGHT PERCENT ZNO, 1 TO 10 WEIGHT PERCENT CUO, 0 TO 7.5 WEIGHT PERCENT PBO, 0 TO 10 WEIGHT PERCENT SIO2, 0 TO 10 WEIGHT PERCENT AL2O3, AND 0 TO 0.2 WEIGHT PERCENT PBF2 AND WHEREIN SAID SOLDER GLASS COMPOSITION HAVING A FIBER SOFTENING POINT TEMPERATURE OF 525 TO 575*C., AND COEFFICIENT OF THERMAL EXPANSION OF 40 TO 50X10**-7 (0-300*C.).
 8. A VITREOUS SOLDER GLASS COMPOSITION WHEREIN SAID GLASS CONSISTS ESSENTIALLY OF 5 TO 30 WEIGHT PERCENT V2O3, 20 TO 40 WEIGHT PERCENT B2O3, 40 TO 60 WEIGHT PERCENT ZNO AND 1 TO 7.5 WEIGHT PERCENT PBO AND WHEREIN SAID GLASS HAS A FIBER SOFTENING POINT OF 525 TO 575*C., AND A COEFFICIENT OF EXPANSION OF 40 TO 50X10**-7 (0-300*C.). 